1. Field of the Invention
The present invention relates to an immersion object detection method for irradiating an electric wave such as a millimeter wave within e.g., a detection area to detect a reflected wave therefrom, thereby detecting existence of the immersion object within the detection area, and an immersion object detection system using such a method.
2. Description of the Background Art
Conventionally, with respect to crime prevention sensors for detecting a human body and the like, various types of sensors such as an infrared sensor, an ultrasonic sensor, an electric wave sensor and the like have been proposed. Among the above-mentioned sensors, the electric wave sensor, which is considerably less susceptible to natural environmental variation factors such as rain, snow and wind even when used outdoors, makes it possible to detect a human body within the detection area with high precision.
With respect to the electric wave sensor that includes various types, an electric wave sensor having the following construction has been disclosed. The electric wave sensor first irradiates an electric wave, in which the frequency has been modulated, to a detection area. Then, it receives a reflected wave of the irradiated electric wave and generates a beat wave by mixing the reflected wave with the original electric wave. This beat wave is spectrum-analyzed to examine the frequency at which a peak exists and the intensity thereof, thereby detecting a human body and the distance therefrom.
Thus, the electric wave sensor is free from the influences of external disturbances due the natural environmental environment factors, and also detects the position of the detected human body, so that this provides excellent performances as a crime prevention sensor.
On the other hand, with respect to the infrared sensor, etc., a regression reflecting type photoelectric sensor for detecting an immersion of an object by using a regression reflecting method. With respect to the regression reflecting method, in the case of an infrared sensor, a reflection plate, etc. is previously placed within a detection area, and an infrared ray is irradiated to this reflection plate, so that by detecting a reflected light from the reflection plate, any immersion of an object such as a human body into the detection area is detected.
As described above, the electric wave sensor detects a human body by examining the frequency at which a peak exists and the intensity thereof in a beat wave that has been spectrum-analyzed. Here, in general, a human body has a low reflectance to an electric wave. Moreover, it has been known that the intensity of the reflected wave decreases in inversely proportional to the distance raised to the fourth power. More specifically, in the case that a human body to be detected is far away from the sensor main body, the intensity of the reflected wave from the human body decreases considerably.
On the other hand, the beat wave obtained by mixing the reflected wave to be received with the original transmission wave contains noise components. These noise components result from a thermal noise in a circuit for generating a transmission wave and in a receiving circuit, a noise caused by a mixer for mixing a reflected wave and a transmission wave and a noise contained in a transmission wave as it own.
Therefore, the wave sensor has a problem that the intensity of the reflected wave from the human body positioned far away from the sensor main body come to reduce to the same level as the intensity of the above-mentioned noise components or a level weaker than the intensity thereof, thereby failing to detect the human body.
On the other hand, the above-mentioned regression reflecting type sensor has a problem that it can detect immersion of any object between the sensor and the reflection plate while it fails to detect how far the immersion object is away from the sensor main body and to identify the immersion object.
The present invention has been devised to solve the above-mentioned problems, and an objective thereof is to provide an immersion object detection method capable of detecting an immersion object within a detection target area irrespective of its short distance/long distance and of specifying the position thereof, and an immersion object detecting system using such a method.
In order to solve the above-mentioned problems, according to a first aspect of the present invention, an immersion object detection method includes the steps of irradiating a wave to a detection target area; detecting a reflected wave from the detection target area by reflected wave detection means; and determining that an immersion object exists within the detection target area in a case that the reflected wave cannot be detected from at least one reflection member among a plurality of reflection members placed within the detection target area, and simultaneously specifying a position of the immersion object in accordance with a position of the reflection member which cannot detect.
In accordance with the above-mentioned method, first, the wave irradiated to the detection target area is reflected in the detection target area, and the reflected wave is detected by the reflected wave detection means. Moreover, a plurality of reflection members are placed within the detection target area. Then, in the above-mentioned method, if there is any reflection member which cannot detect by the reflected wave detection means, a detecting operation of the immersion object and a specifying operation of the position thereof are carried out.
Here, if the reflection members are made of a material having high reflectance to the wave, it is possible to detect the reflected wave from a wider range as compared with a case in which, e.g., the reflected wave from the immersion object itself are detected. Moreover, in accordance with the position of the reflection member which cannot detect, the position of the immersion object is specified so that it becomes possible to provide the detection target area as a wider area, and also to specify the position of the immersion object.
Moreover, depending on the kind of the wave and the performance of the reflected wave detection means, in some cases, it is not possible to specify the position of the immersion object based on only the directly reflected wave from the immersion object. However, the application of the above-mentioned method makes it possible to specify the position of the immersion object even in such a case.
Furthermore, according to the first aspect, the immersion object detection method is characterized in that the plurality of reflection members are placed such that distances from the reflected wave detection means to each of the reflection members are different, respectively, and the position of the immersion object is specified as any position between a reflection member having the furthest distance from the reflected wave detection means among the reflection members which can detect the reflected wave and a reflection member having the nearest distance from the reflected wave detection means among the reflection members which cannot detect the reflected wave.
In the above-mentioned method, the plurality of reflection members are placed such that the distances from the reflected wave detection means to the respective reflection members are different, respectively. In the case an immersion object exists within the detection target area in this state, the reflected wave from the reflection member placed in a position closer to the reflected wave detection means than the immersion object are detected, while the reflected wave from the reflection member placed in a position farther from the reflected wave detection means than the immersion object are not detected because they are shielded by the immersion object. By utilizing this fact, the above-mentioned method specifies the position of the immersion object. Therefore, it becomes possible to accurately specify the position of the immersion object by using a comparatively simple analysis.
Furthermore, according to the first aspect of the present invention, the immersion object detection method is characterized in that the plurality of reflection members are placed such that at least one reflection member among the plurality of reflection members has a different direction with respect to the reflected wave detection means as compared with the other reflection members.
In the above-mentioned method, the reflection member is provided in a different direction with respect to the reflected wave detection means. At this time, if the reflected wave detection means cannot detect the reflected wave from the reflection member provided in a certain direction, and then cannot detect the reflected wave from a reflection member provided in a different direction, it is determined that the immersion object has moved from the certain direction to another direction with respect to the reflected wave detection means. Thus, the above-mentioned immersion object detection method makes it possible to specify the moving direction of an immersion object.
Furthermore, according to the first aspect of the present invention, the immersion object detection method is characterized in that in a case that the immersion object exists in a short-distance area having a distance of not more than a predetermined value from the reflected wave detection means, the position of the immersion object is specified by analyzing a directly reflected wave from the immersion object, and in a case that the immersion object exists in a long-distance area having a distance of not less than a predetermined value from the reflected wave detection means, the position of the immersion object is specified in accordance with the position of the reflection member which cannot detect.
In the above-mentioned method, when the immersion object exists in the short-distance area, the position of the immersion object is specified by the directly reflected wave from the immersion object, while when the immersion object exists in the long-distance area, the position of the immersion object is specified in accordance with the position of the reflection member which cannot detect. More specifically, in a short-distance in which a sufficient intensity of the reflected wave is ensured, the position is precisely detected by the directly reflected wave from the immersion object, while in a long-distance in which the intensity of reflected wave becomes weaker, the position is detected based on the reflected wave from the reflection member as described above.
Therefore, as compared with a case in which the position is only specified by the directly reflected wave from the immersion object, it becomes possible to detect the immersion object in an area covering wider range. Moreover, in the short distance in which more detailed information is required than the case in which only the position detection is carried out based on the reflected wave from the reflection member, it becomes possible to more precisely detect the position of the immersion object.
Moreover, even when the specifying method of the position of the immersion object is changed in accordance with the distance from the reflected wave detection means, it is not necessary to change the kind of the wave irradiated from a wave irradiation means or to change the kind of the wave detected by the reflected wave detection means. More specifically, the detection of the immersion object can be carried out from the short distance to the long distance by using a single system so that it is possible to reduce the costs and also to reduce the system scale as compared with a case in which, e.g., a plurality of systems are installed depending on distances.
Furthermore, according to the first aspect of the present invention, the immersion object detection method includes the steps of: placing a reference object for comparing with the immersion object in the short-distance area within the detection target area; irradiating the wave to the detection target area, thereby detecting the reflected wave from the reference object by the reflected wave detection means; and creating reference object information based on the reflected wave to be detected, wherein in the case that the immersion object exists in the short-distance area, the position of the immersion object is specified, and the reference object information is compared with immersion object information created based on the reflected wave from the immersion object detected by the reflected wave detection means, thereby specifying the kind of the immersion object. The above-mentioned feature is also applied to a second aspect of the present invention which will be described below.
Here, the reference object is desirable to use a member which is a target to be detected in its immersion within the detection target area. Moreover, in the case when a plurality of objects to be detected in their immersion exist, it is preferable to create reference object information for each of the objects.
In accordance with the above-mentioned method, the kind of the immersion object is specified by comparing the current information detected by the reflected wave detection means with the reference object information. Thus, a controlling operation is available in which even when an object other than the object which is a target to be detected in its immersion enters the detection target area, this object is not dealt as an immersion object. Consequently, it is possible to reduce erroneous detection.
Furthermore, according to the first aspect of the present invention, the immersion object detection method is characterized in that the wave to be irradiated is an electric wave. The above-mentioned feature is also applied to the second aspect of the present invention which will be described below.
In the above-mentioned method, since the electric wave is irradiated to the detection target area to detect any immersion object, the method is less susceptible to adverse effects to detection, such as bad visibility due to rain, fog, snow, etc., and bad visibility due to smoke pot used by a dubious character so as to intervene detection. Moreover, since the electric wave has the property of passing through objects, the reflection member to be placed within the detection target area may be placed, e.g., under ground or inside a wall. Thus, it becomes possible to construct an immersion object detection system without giving adverse effects to the environment.
Moreover, in the case of irradiation of the electric wave, by detecting the directly reflected wave from the immersion object, the position of the immersion object can be specified. Furthermore, by analyzing the level of the directly reflected wave from the immersion object, it is possible to specify the kind of the immersion object.
Furthermore, according to the first aspect of the present invention, the immersion object detection method includes the steps of: irradiating the wave to the detection target area in a state that no immersion object exists within the detection target area, thereby detecting the reflected wave from the reflection member by the reflected wave detection means; and creating normal state information with respect to the reflection member based on the reflected wave to be detected, wherein the reflection member which cannot detect is specified by comparing the normal state information with information created based on the reflected wave detected by the reflected wave detection means. The above-mentioned feature is also applicable to the second and third aspects of the present invention which will be described below.
In the above-mentioned method, by comparing the current information detected by the reflected wave detection means with the normal state information, the reflection member which cannot detect is specified. Therefore, since the reflection member which cannot detect is accurately specified, it is possible to detect an immersion object and to specify the position thereof accurately.
According to the second aspect of the present invention, the immersion object detection method includes the steps of irradiating a wave to a detection target area; detecting a reflected wave from the detection target area by reflected wave detection means; determining that an immersion object exists within the detection target area in a case that the reflected wave cannot be detected from one reflection member placed within the detection target area, and simultaneously specifying a position of the immersion object in accordance with a position of the reflection member which cannot detect, wherein the position of the immersion object is specified by analyzing a directly reflected wave from the immersion object in a case that the immersion object exists in a short-distance area having a distance of not more than a predetermined value from the reflected wave detection means, while in a case that the immersion object exists in a long-distance area having a distance of not less than the predetermined value from the reflected wave detection means, the reflected wave cannot be detected from the reflection member by the reflected wave detection means, so that existence of the immersion object is specified between a position in which a distance from the reflected wave detection means is the predetermined value and a position where the reflection member is placed.
In the above-mentioned method, first, the wave is reflected within the detection target area, and the reflected wave is detected by the reflected wave detection means. Here, one reflection member is placed within the detection target area. Then, in the above-mentioned method, in the case that an immersion object exists in the short-distance area, the position of the immersion object is specified by using the directly reflected wave from the immersion object, and in the case that an immersion object exists in the long-distance area, the reflection member cannot detect by the reflected wave detection means, thereby specifying the position of the immersion object at the long distance area between the position of the reflected wave detection means and the reflection member.
In other words, in a short-distance in which a sufficient intensity of the reflected wave is ensured, the position of the immersion object is precisely detected by using the directly reflected wave therefrom, while in a long-distance in which the intensity of reflected wave becomes weaker, the position is detected based on the reflected wave from the reflection member as described above. Therefore, as compared with a case in which the position is specified by using only the directly reflected wave from the immersion object, it becomes possible to detect the immersion object in an area covering wider range. Moreover, in the short distance in which more detailed information is required than the case in which only the position detection is carried out based on the reflected wave from the reflection member, it becomes possible to more precisely detect the position of the immersion object.
Moreover, even when the specifying method of the position of the immersion object is changed in accordance with the distance from the reflected wave detection means, it is not necessary to change the kind of wave irradiated from the wave irradiation means or to change the kind of wave detected by the reflected wave detection means. In other words, the detection of the immersion object can be carried out from the short distance to the long distance by using a single immersion object detection system using the above-mentioned method so that it is possible to reduce the costs and also to reduce the system scale as compared with cases in which, e.g., a plurality of systems are placed in accordance with distances.
According to a third aspect of the present invention, the immersion object detection method includes the steps of: irradiating a wave to a detection target area; detecting a reflected wave from the detection target area by reflected wave detection means; and determining that an immersion object exists within the detection target area in a case that the reflected wave cannot be detected from one reflection member placed within the detection target area, wherein the wave to be irradiated is an electric wave.
In the above-mentioned method, first, the above-mentioned electric wave is reflected within the detection target area, and the reflected wave is detected by the reflected wave detection means. Here, one reflection member is placed within the detection target area. Then, in the above-mentioned method, if there is a reflection member which cannot detect by the reflected wave detection means, any immersion object is detected.
Here, when the reflection members are made of a material having high reflectance to the electric wave irradiated by the wave irradiation means, it is possible to detect the reflected wave from a wider area as compared with a case in which, e.g., the reflected wave from the immersion object itself is detected. Moreover, since the position of the immersion object is specified in accordance with the position of the reflection member which cannot detect, it becomes possible to set the detection target area as a wider area.
In the above-mentioned method, electric wave is irradiated to the detection target area, thereby detecting any immersion object. As described above, since the electric wave has the property of passing through objects, the method is less susceptible to adverse effects to detection, such as bad visibility due to rain, fog, snow, etc., and bad visibility due to smoke pot used by a dubious character so as to intervene detection. Moreover, the reflection member placed within the detection target area may be placed, e.g., under ground or inside a wall, so that it becomes possible to construct an immersion object detection system without giving adverse effects to the environment. In addition, as compared with a case using a light, an infrared ray, etc., it is possible to set a wider detection target area (e.g., approximately 100 m).
Moreover, in the case of the application of the electric wave, even when dusts, etc. adhere to the reflection member, the effects thereof exerted when the reflected wave from the reflection member is detected by the reflected wave detection means is so small that no problems are raised in practical use. Thus, it is possible to eliminate the maintenance of the reflection members.
According to a fourth aspect of the present invention, an immersion object detection system includes: wave irradiation means of irradiating a wave to a detection target area; a plurality of reflection members placed within the detection target area; reflected wave detection means in which the wave irradiated from the wave irradiation means detects a reflected wave from the detection target area; and immersion object detection means of detecting an immersion object within the detection target area, wherein in a case that the reflected wave detection means cannot detect the reflected wave from at least one reflection member among the plurality of reflection members, the immersion object detection means determines that the immersion object exists within the detection target area and specifies a position of the immersion object in accordance with a position of the reflection member which cannot detect.
In accordance with the above-mentioned constitution, first, the wave irradiated by the wave irradiation means is reflected within the detection target area, and the reflected wave is detected by the reflected wave detection means. Here, a plurality of reflection members are placed within the detection target area. Then, if there is any reflection member which cannot detect by the reflected wave detection means, the reflected wave detection means detects the immersion object and specifies the position thereof.
Here, when the reflection members are made of a material having high reflectance to the wave irradiated from the wave irradiation means, it is possible to detect the reflected wave from a wider area as compared with a case in which, e.g., the reflected wave from the immersion object itself is detected. Moreover, the position of the immersion object is specified in accordance with the position of the reflection member which cannot detect, so that it becomes possible to set the detection target area as a wider area, and also to specify the position of the immersion object.
Moreover, depending on the kind of the wave and the performance of the reflected wave detection means, in some cases, it is not possible to specify the position of the immersion object only based on the directly reflected wave from the immersion object. However, the application of the above-mentioned method makes it possible to specify the position of the immersion object even in such a case.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that the plurality of reflection members are placed such that distances from the reflected wave detection means to each of the reflection members are different, respectively, and the immersion object detection means determines that the immersion object exists between a reflection member having a furthest distance from the reflected wave detection means among the reflection members which can detect the reflected wave and a reflection member having a nearest distance from the reflected wave detection means among the reflection members which cannot detect the reflected wave.
In the above-mentioned constitution, the plurality of reflection members are placed such that the distances from the reflected wave detection means to each of the reflection members are different, respectively. In the case that any immersion object exists within the detection target area in this state, the reflected wave from the reflection members placed in positions closer to the reflected wave detection means than the immersion object is detected, while the reflected wave from the reflection members placed in positions farther from the reflected wave detection means than the immersion object is not detected because they are shielded by the immersion object. By utilizing this fact, the immersion object detection means specifies the position of the immersion object. Therefore, it becomes possible to accurately specify the position of the immersion object by using a comparatively simple analysis.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that the plurality of reflection members are placed such that at least one reflection member among the plurality of reflection members has a different direction with respect to the reflected wave detection means as compared with the other reflection members.
In the above-mentioned constitution, the reflection member is provided in a different direction with respect to the reflection wave detecting means. At this time, when the reflected wave detection means cannot detect the reflected wave from the reflection member provided in a certain direction, and then cannot detect the reflected wave from a reflection member provided in a different direction, the immersion object detection means can determine that the immersion object has moved from the certain direction to another direction with respect to the reflected wave detection means. Thus, the above-mentioned immersion object detection system makes it possible to specify the moving direction of an immersion object.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that in a case that the immersion object exists in a short-distance area where a distance from the reflected wave detection means is not more than a predetermined value, the immersion object detection means specifies the position of the immersion object by analyzing a directly reflected wave from the immersion object, and in a case that the immersion object exists in a long-distance area where a distance from the reflected wave detection means is not less than the predetermined value, the immersion object detection means specifies the position of the immersion object in accordance with the position of the reflection member which cannot detect.
In the above-mentioned constitution, in the case that an immersion object exists in the short-distance area, the position thereof is specified by analyzing the directly reflected wave from the immersion object, and in the case that an immersion object exists in the long distance area, the position thereof is specified in accordance with the position of the reflection member which cannot detect. In other words, in a short-distance in which a sufficient intensity of the reflected wave is ensured, the position is precisely detected by using the directly reflected wave from the immersion object, while in a long-distance in which the intensity of the reflected wave becomes weaker, the position is detected based on the reflected wave from the reflection member as described above. Therefore, as compared with a case in which the position is specified by using only the directly reflected waves from the immersion object, it becomes possible to detect an immersion object in an area covering wider range. Moreover, in the short distance in which more detailed information is required than the case in which only the position is detected based on the reflected wave from the reflection member, it becomes possible to more precisely detect the position of an immersion object.
Moreover, even when the specifying method of the position of an immersion object is changed depending on the distance from the reflected wave detection means, it is not necessary to change the kind of the wave irradiated from the wave irradiation means or to change the kind of wave detected by the reflected wave detection means. In other words, the detection of an immersion object can be carried out from the short distance to the long distance by using a single system so that it is possible to reduce the costs and also to reduce the system scale as compared with a case in which, e.g., a plurality of systems are placed depending on distances.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system further includes a storage means of previously placing a reference object for comparing with the immersion object in the short-distance area within the detection target area, thereby storing reference object information of the reflected wave from the reference object detected by the reflected wave detection means, wherein the immersion object detection means compares the reference object information stored in the storage means with information detected by the reflected wave detection means in a case that the immersion object is detected in the short-distance area, thereby specifying the kind of the immersion object. The above-mentioned feature is also applied to a fifth aspect of the present invention which will be described below.
In accordance with the above-mentioned constitution, the immersion object detection means compares current information detected by the reflected wave detection means with the reference object information stored in the storage means so that the kind of the immersion object is specified. Thus, a controlling operation can be carried out even when an object other than the object which is a target to be detected in its immersion enters the detection target area, this object is not dealt as an immersion object. Consequently, it is possible to reduce erroneous detection.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that the wave to be irradiated is an electric wave. The above-mentioned feature is also applied to the fifth aspect of the present invention which will be described below.
In the above-mentioned constitution, since the electric wave is irradiated to the detection target area to detect the immersion object, the method is less susceptible to adverse effects to detection, such as bad visibility due to rain, fog, snow, etc., and bad visibility due to smoke pot used by a dubious character so as to intervene detection. Moreover, since the electric wave has the property of passing through objects, the reflection member to be placed within the detection target area may be placed, e.g., under ground or inside a wall. Thus, it becomes possible to construct an immersion object detection system without giving adverse effects to the environment.
Moreover, in the case of irradiation of the electric wave, the position of the immersion object can be specified by detecting the directly reflected wave from the immersion object. Furthermore, by analyzing the level of the directly reflected wave from the immersion object, it is possible to specify the kind of the immersion object.
Furthermore, in the fourth aspect of the present invention, the immersion object detection system further includes a storage means of storing normal state information of the reflected wave from the reflection member, detected by the reflected wave detection means, in a state that no immersion object exists within the detection target area, wherein the immersion object detection means compares the normal state information stored in the storage means with information detected by the reflected wave detection means, thereby specifying the reflection member which cannot detect. The above-mentioned feature is also applicable to the fifth and sixth aspects of the present invention which will be described below.
In the above-mentioned constitution, the immersion object detection means compares the current information detected by the reflected wave detection means with the normal state information stored in the storage means to specify the reflection member which cannot detect. Therefore, since the reflection member which cannot detect is accurately specified, it is possible to detect an immersion object and to specify the position thereof accurately.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that the reflection members are placed within a range of a predetermined height from the ground surface. The above-mentioned feature is also applicable to the fifth and sixth aspects of the present invention which will be described below.
In accordance with the above-mentioned constitution, since the reflection members are placed within the range having a predetermined height from the ground surface, any immersion object in the detection target area with a height level other than the range having the predetermined height is not detected. Therefore, e.g., by setting the range of the predetermined height to the height range from the abdomen to the chest of the human body, it is possible to limit the object to be detected in its immersion to a human body without detecting small animals such as dogs and cats. Consequently, it becomes possible to eliminate the possibility of detection of unnecessary immersion objects.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that the reflection members are objects previously placed within the detection target area. The above-mentioned feature is also applicable to the fifth and sixth aspects of the present invention which will be described below.
In accordance with the above-mentioned constitution, since the objects previously placed within the detection target area are used as the reflection members, it is not necessary to newly place reflection members. Thus, it becomes possible to reduce the costs required for constructing the immersion object detection system, and also to provide the immersion object detection system without causing adverse effects on the environment.
Furthermore, according to the fourth aspect of the present invention, the immersion object detection system is characterized in that a deflection means of deflecting a course of the wave irradiated by the wave irradiation means is provided between the wave irradiation means and the reflection members. The above-mentioned feature is also applicable to the fifth and sixth aspects of the present invention which will be described below.
Here, xe2x80x9cdeflectionxe2x80x9d refers to the function for changing the course direction of the wave by utilizing factors such as reflection, refraction or diffraction of wave. With respect to the deflection means, e.g., members such as flat-surface reflection plates may be preferably used.
In accordance with the above-mentioned constitution, the detection target area is provided in a non-linear form so that even the entire periphery of a building or a winding place having bad visibility may be set as the detection target area. In other words, the single system can be applied to areas having various shapes, so that it becomes possible to reduce the costs and scale of the system as compared with a case in which a plurality of systems are placed in respective linear detection areas.
According to the fifth aspect of the present invention, the immersion object detection system includes: wave irradiation means of irradiating a wave to a detection target area; a reflection member placed within the detection target area; reflected wave detection means in which the wave irradiated from the wave irradiation means detects the reflected wave from the detection target area; and immersion object detection means of detecting the immersion object within the detection target area, wherein in a case that the immersion object exists in a short-distance area where a distance from the reflected wave detection means is not more than a predetermined value, the immersion object detection means specifies a position of the immersion object by analyzing a directly reflected wave from the immersion object, and in a case that the immersion object exists in a long-distance area where a distance from the reflected wave detection means is not less than the predetermined value, the reflected wave detection means cannot detect the reflected wave from the reflection member, so that the immersion object detection means specifies that the immersion object exists between a position in which a distance from the reflected wave detection means is the predetermined value and a position where the reflection member is placed.
In accordance with the above-mentioned constitution, first, the wave irradiated by the wave irradiation means is reflected within the detection target area, and the reflected wave is detected by the reflected wave detection means. Here, one reflection member is placed within the detection target area. In the case that an immersion object exists in the short-distance area, the immersion object detection means specifies the position of the immersion object by using directly reflected wave from the immersion object, and in the case that an immersion object exists in the long-distance area, the reflection member cannot detect by the reflected wave detection means, the immersion object detection means specifies the position of the immersion object at the long distance area between the position of the reflected wave detection means and the reflection member.
In other words, in a short-distance in which a sufficient intensity of the reflected wave is ensured, the position is precisely detected by using the directly reflected wave from the immersion object, while in a long-distance in which the intensity of the reflected wave becomes weaker, the position is detected based on the reflected wave from the reflection member as described above. Therefore, as compared with a case in which the position is specified by using only the directly reflected wave from the immersion object, it becomes possible to detect an immersion object in an area covering wider range. Moreover, in the short distance in which more detailed information is required than the case in which only the position detection is carried out based on reflected waves from the reflection member, it becomes possible to more precisely detect the position of an immersion object.
Moreover, even when the specifying method of the position of an immersion object is changed in accordance with the distance from the reflected wave detection means, it is not necessary to change the kind of the wave irradiated from the wave irradiation means or to change the kind of the wave detected by the reflected wave detection means. In other words, an immersion object can be detected from the short distance to the long distance by using a single immersion object detection system using the above-mentioned method so that it is possible to reduce the costs and also to reduce the system scale as compared with a case in which, e.g., a plurality of systems are placed depending on distances.
According to the sixth aspect of the present invention, the immersion object detection system includes: wave irradiation means of irradiating a wave to a detection target area; a reflection member placed within the detection target area; reflected wave detection means in which the wave irradiated from the wave irradiation means detects the reflected wave from the detection target area; and immersion object detection means of detecting the immersion object within the detection target area, wherein the wave irradiated from the wave irradiation means is an electric wave, and in a case that the reflected wave detection means cannot detect the reflected wave from the reflection member, the immersion object detection means determines that the immersion object exists within the detection target area, and the immersion object detection means specifies that the immersion object exists between a position of the reflected wave detection means and a position of the reflection member.
In accordance with the above-mentioned constitution, first, the electric wave irradiated by the wave irradiation means is reflected within the detection target area, and the reflected wave is detected by the reflected wave detection means. Here, one reflection member is placed within the detection target area. Then, in the case that there is the reflection member which cannot detect by the reflection wave detection means, the immersion object detection means detects the immersion object and specifies the position thereof
Here, when the reflection members are made of a material having high reflectance to the electric wave irradiated from the wave irradiation means, it is possible to detect the reflected wave from a wider area as compared with a case in which, e.g., the reflected wave from the immersion object itself is detected. Moreover, the position of the immersion object is specified in accordance with the position of the reflection member which cannot detect, so that it becomes possible to set the detection target area as a wider area, and also to specify the position of the immersion object.
In the above-mentioned constitution, the electric wave is irradiated to the detection target area to detect an immersion object. As described above, since the electric wave has the property of passing through objects, the system is less susceptible to adverse effects to detection, such as bad visibility due to rain, fog, snow, etc., and bad visibility due to smoke pot used by a dubious character so as to intervene detection. Moreover, the reflection member placed within the detection target area may be placed, e.g., under ground or inside a wall. Thus, it becomes possible to construct an immersion object detection system without giving adverse effects to the environment. Moreover, as compared with a case using a light, an infrared ray, etc., it is possible to provide a wider detection target area (e.g., approximately 100 m).
In the case of the application of the electric wave, even when dusts, etc. adhere to the reflection member, the effects thereof exerted when reflected waves from the reflection member are detected by the reflected wave detection means are so small that no problems are raised in practical use. Thus, it is possible to eliminate the maintenance of the reflection members.